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libbpf: add tracepoint attach API
Allow attaching BPF programs to kernel tracepoint BPF hooks specified by category and name. Signed-off-by: Andrii Nakryiko <andriin@fb.com> Acked-by: Song Liu <songliubraving@fb.com> Reviewed-by: Stanislav Fomichev <sdf@google.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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@ -4190,6 +4190,85 @@ struct bpf_link *bpf_program__attach_uprobe(struct bpf_program *prog,
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return link;
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}
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static int determine_tracepoint_id(const char *tp_category,
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const char *tp_name)
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{
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char file[PATH_MAX];
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int ret;
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ret = snprintf(file, sizeof(file),
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"/sys/kernel/debug/tracing/events/%s/%s/id",
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tp_category, tp_name);
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if (ret < 0)
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return -errno;
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if (ret >= sizeof(file)) {
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pr_debug("tracepoint %s/%s path is too long\n",
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tp_category, tp_name);
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return -E2BIG;
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}
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return parse_uint_from_file(file, "%d\n");
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}
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static int perf_event_open_tracepoint(const char *tp_category,
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const char *tp_name)
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{
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struct perf_event_attr attr = {};
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char errmsg[STRERR_BUFSIZE];
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int tp_id, pfd, err;
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tp_id = determine_tracepoint_id(tp_category, tp_name);
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if (tp_id < 0) {
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pr_warning("failed to determine tracepoint '%s/%s' perf event ID: %s\n",
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tp_category, tp_name,
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libbpf_strerror_r(tp_id, errmsg, sizeof(errmsg)));
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return tp_id;
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}
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attr.type = PERF_TYPE_TRACEPOINT;
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attr.size = sizeof(attr);
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attr.config = tp_id;
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pfd = syscall(__NR_perf_event_open, &attr, -1 /* pid */, 0 /* cpu */,
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-1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
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if (pfd < 0) {
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err = -errno;
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pr_warning("tracepoint '%s/%s' perf_event_open() failed: %s\n",
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tp_category, tp_name,
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libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
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return err;
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}
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return pfd;
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}
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struct bpf_link *bpf_program__attach_tracepoint(struct bpf_program *prog,
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const char *tp_category,
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const char *tp_name)
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{
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char errmsg[STRERR_BUFSIZE];
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struct bpf_link *link;
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int pfd, err;
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pfd = perf_event_open_tracepoint(tp_category, tp_name);
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if (pfd < 0) {
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pr_warning("program '%s': failed to create tracepoint '%s/%s' perf event: %s\n",
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bpf_program__title(prog, false),
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tp_category, tp_name,
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libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
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return ERR_PTR(pfd);
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}
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link = bpf_program__attach_perf_event(prog, pfd);
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if (IS_ERR(link)) {
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close(pfd);
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err = PTR_ERR(link);
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pr_warning("program '%s': failed to attach to tracepoint '%s/%s': %s\n",
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bpf_program__title(prog, false),
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tp_category, tp_name,
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libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
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return link;
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}
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return link;
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}
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enum bpf_perf_event_ret
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bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
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void **copy_mem, size_t *copy_size,
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@ -178,6 +178,10 @@ LIBBPF_API struct bpf_link *
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bpf_program__attach_uprobe(struct bpf_program *prog, bool retprobe,
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pid_t pid, const char *binary_path,
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size_t func_offset);
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LIBBPF_API struct bpf_link *
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bpf_program__attach_tracepoint(struct bpf_program *prog,
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const char *tp_category,
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const char *tp_name);
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struct bpf_insn;
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@ -171,6 +171,7 @@ LIBBPF_0.0.4 {
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bpf_object__load_xattr;
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bpf_program__attach_kprobe;
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bpf_program__attach_perf_event;
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bpf_program__attach_tracepoint;
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bpf_program__attach_uprobe;
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btf_dump__dump_type;
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btf_dump__free;
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